The present invention relates to a tile according to the preamble of claim 1.
Ceramic tiles have long been used for finishing walls and floors in buildings. Important properties of such tiles are that they can be placed easily using adhesive mortar and that these tiles have a hard and water impervious surface. Tiled surfaces may furthermore be covered with tiles of appropriate colours and patterns for aesthetic appeal.
It has also been known to manufacture tiles of coloured, opaque glass, such tiles being used in mosaics for example.
Due to the inner structure of ceramic tiles, the colour coating of such tiles is naturally given by the composition of the glaze. Accordingly, the colour effect is always superficial. Even on penetratingly coloured glass tiles, the colour effect is merely superficial, since the rays of light cannot penetrate inside the glass layer to a noteworthy extent. Another drawback of conventional glass tiles is that they cannot be trimmed with the commonly available means for tiling. Such glass tiles therefore are especially suitable for being used in mosaics since here, the individual tile must not be trimmed. On tiling surfaces with tiles having a conventional size, e.g., 20xc3x9730 cm, the shape of a plurality of tiles has to be trimmed to conform to corners in a room, doors, windows, switches, fittings and the like. Since a majority of tilers are not equipped with the tools and do not dispose of the know-how of those skilled in the art of glass working, tiling with glass tiles has not been hereto before possible on a commercial scale.
The document AT 304 033 B relates to panes, panels, tiles, tesserae made of transparent glass, the rear side of which is provided with a coating of natural or artificial fish silver.
This permits to achieve novel optical and aesthetic effects when such panels are used as tesserae for example. In no event however is it possible to trim them like tiles owing to the structure of the glass.
The GB 2 271 529 A discloses a glass tile which has a rear side that is provided with a layer of glue and that finally has thereupon a coating of magnesium oxide. Such a glass tile has a very complicated multilayered structure that renders its manufacturing complicated and expensive. Additionally, such a tile cannot be trimmed for tiling due to the given properties of glass, i.e., the cutting out of recesses or the trimming of the tile is extremely complicated.
The object of the present invention is to provide a tile that, in its optical appearance, is clearly defined over conventional tiles and that can be trimmed in principle in the same way as a ceramic tile.
The solution of these objects is to submit the glass layer to a heat treatment until it begins to soften and that the coloured layer consists of a mineral lacquer.
By thermally treating the glass layer, a microstructural change occurs that permits to break the glass in a controlled way during the trimming process. Stated in general terms, two different processing operations occur in the tiling process: in a first processing operation a tile must be cut along a straight line, this being usually performed by having the tile scribed along the parting line by means of a cutting wheel made of a hard metal prior to breaking it. The other type of processing operation is necessary when a recess must be provided in a tile, for a switch, a socket or a sanitary connection for example. In such cases, the tweaking out of the recess is often accomplished by means of appropriately shaped pliers (glazier""s pliers) or with water-cooled diamond cutting wheels. With the tile according to the invention, both types of processing operations may be conducted in a way essentially analogous to the way ceramic tiles are processed. As a result, the tile according to the invention can be processed by tilers without requiring any particular measures. The performing of accurate borings is the only action that is somewhat more complicated on the tiles of the invention than on ceramic tiles.
Another major point of the invention is that the coat of lacquer is not attacked by the adhesive mortar used for tiling. This means that during tiling, the coat of lacquer does not react chemically with the strongly alkaline adhesive mortar, which leads for example to a change in colour or which causes the coat of lacquer to detach from the layer of glass.
The tile according to the invention makes it possible to realize an appearance which differs completely from that of conventional tiles. Since the structure of the colours constituting the pattern of the tile is located behind a transparent layer of glass, a three-dimensional aspect of the tile is created. Through various refraction effects and the like, effects are obtained which cannot be observed on conventional tiles.
In principle, it is possible to utilize for the coloured layer a two-component enamel. A two-component acrylic enamel as it has specifically been evolved for the overall or partial paintwork of utility vehicles, road tank cars, buses and the like, would be particularly suitable therefor. Important features within the spirit of the invention are the high mechanical and chemical stability and the durable gloss-life as well as the fastness to petrol, fats and other solvents. Mineral lacquers perfectly fulfill these conditions. It is preferably question of enamel varnishes, i.e., glass powder into which pigments have been incorporated and which is made pasty for application by screen printing.
The three-dimensional structural effect of the inventive tile can still be enhanced by the fact that the surfaces of the glass layer are not smooth. By structuring the surfaces, i.e., by giving them an undulated design, particularly interesting effects are achieved from an aesthetical point of view.
In addition to the coloured layer applied onto the rear side of the glass layer, said layer of glass can also be provided with an internal colour structure. This means that the glass is coloured entirely or at specific places. It must be made certain that the glass be transparent at least in some areas in order to achieve the effects described above.
The coat of lacquer is preferably roughed in a drying treatment. This means that the coloured layer per se is provided on its outer surface with a microscopic roughness. This roughness, as contrasted with the optional structure given to the surface of the glass, which is in the order of millimeters, has practically no optical influence on the appearance of the placed tile. The bond of adhesive mortar or the like however is considerably enhanced so that secure tiling is made certain.
The invention furthermore relates to a method for manufacturing a tile, the method involving the following steps:
cutting of a glass pane on a section to the desired shape of the tile,
heat treatment of the section until it softens,
cooling of the section to a temperature in the range of room temperature,
application of a coat of mineral lacquer to one side of the section, and
firing of the coat of lacquer at a temperature which is lower than the maximum temperature of the heat treatment.
Preferably, the softening point of the glass should be exceeded in the heat treatment. In general, this is achieved by heating to a maximum temperature ranging from 750xc2x0 to 850xc2x0.
During the cooling phase it is advantageous to provide for several AC-points in order to achieve the most advantageous structure of the glass. In a particularly preferred embodiment of the method according to the invention, the heat treatment is conducted while the piece is laid on a bed of moulding sand, wherein a particular three-dimensional effect can be obtained when the bed of pulverized asbestos is given a structure prior to placing the piece there onto, wherein the structure may be achieved by pressing a pattern into the bed of sand by means of a stamp or a roller.
Customarily, heat treatment is carried out by placing the glass panes to be treated into the cold furnace. This furnace is then heated to the maximum temperature, which depends on the type of glass and the thickness of the material. The essential point with heat treatment is the cooling phase, in which various Ac-points must be provided for. By providing these Ac-points, it is possible to have the finished glass tile largely stress-relieved, which is essential for further processing and for durability. In the following example of an embodiment, a typical process sequence for heat treatment is illustrated on a glass tile 8 mm thick:
Upon completion of heat treatment, the section is cooled to room temperature and is printed, e.g., in a screen-printing method, with an enamel lacquer. Immediately after the printing procedure, the tile is dried in an infrared tunnel kiln at a temperature of about 180xc2x0 C. The dwell time is of approximately 30 seconds. The instant action of heat effects a fast dehydration of the lacquer, the lacquer surface being roughed to a microscopic scale as a result thereof. When several coloured layers are applied to the tile, drying treatment is performed immediately upon the application of each of the coloured layers. Once the last coloured layer has been applied and dried, a protective coating is applied to the tile, firing is carried out at a temperature of about 580xc2x0 C. to about 620xc2x0 C. This temperature is maintained for about 20 minutes. The protective coating on light tiles is generally white, otherwise black, and serves to prevent the surface upon which the tiles have been laid from shining through. The colours are definitively fixated by firing. It is important that the tile cools down in the closed furnace over a period of about 3 to 4 hours or more once firing is over. Thus, unwanted hardening of the glass may be prevented. With this treatment, the roughed structure is preserved, which provides for the excellent stability in processing.
The invention is explained in more detail with the help of an embodiment illustrating an example and represented in the FIGURE.